1. The Field of the Invention
The present invention relates to commercial and mining explosives which are substantially free of nitrates. More particularly, the present invention relates to explosives which do not contribute substantial to oxides of nitrogen emissions to the air, or nitrates to water, or land surrounding their use.
2. Technical Background
Nearly all commercial and mining explosives used in the world today are based on ammonium nitrate or combinations of ammonium nitrate with other alkaline and/or alkaline earth nitrate salts, such as sodium or calcium nitrate. Most explosives of this type rely on the energetic reaction of nitrogen compounds incorporated within the explosive to provide the necessary explosive power.
As a result of the high nitrogen content of these explosives, substantial nitrogen emissions are produced upon detonation. Explosives of this type have the potential to pollute land, water, and air with excess nitrogen containing compounds. Indeed, nitrogen emissions into ground water are frequently observed following use of these types of explosives. Also observed are significant levels of nitrogen oxide emissions into the air. Overall, it is found that the use of conventional mining and commercial explosives can release sufficient amounts oxides of nitrogen into the air and nitrates into water to noticeably degrade the surrounding environment.
Stricter environmental laws regulating emissions of nitrates into the water are being enacted on both the federal and state levels of government. Nitrates such as those used in and emitted by commercial and mining explosives are known to contribute nitrogen compounds to the water in such a manner that they are covered by these federal and state environmental regulations.
Likewise, laws governing the permissible emission of noxious fumes are being tightened. One of the primary areas of air pollution regulation relates to nitrogen oxide (NO.sub.x) emissions. NO.sub.x emissions are regulated and closely monitored because they are known to be some of the primary contributors to smog in urban areas. Thus, the emissions produced by detonation of conventional commercial or mining explosives may be covered by these regulations as well, particularly if the explosives are used in populated areas.
Fortunately, most mines, construction sites, and other operations where blasting takes place, are located in relatively remote areas. In these areas levels of ground water nitrates are often rapidly diluted to acceptable concentrations. In addition, NO.sub.x is less of a concern outside urban areas because there are fewer air pollution emission sources in such areas. In these areas the gaseous fumes produced in blasting operations generally dissipate and cause no immediate problem. However, emission of nitrogen oxides is still a concern in that the overall environment is being slowly degraded even from these remote and relatively small releases of nitrogen oxides.
There are occasional needs for blasting and mining operations even in relatively urbanized areas. These operations include construction of large buildings and construction and repair of roadways. A specific example relates to the production of rock base for construction uses. In certain hard rock granite quarries the blasted granite is crushed and fed through a kiln where it is mixed with asphalt to form road base. The fumes emanating from the stacks of this type of kiln have been tested by environmental authorities and occasionally found to exceed the permissible limits for NO.sub.x. These nitrate emissions could come from several sources, some of which are directly linked to blasting operations. Such sources include, for example: spilled explosive around the borehole or between the boreholes during the explosive loading procedure; explosive in the borehole which did not detonate because it was not formulated properly or it mixed with ground water in the borehole, dissolving some of the nitrates which subsequently were not consumed in the detonation reaction; explosive material trapped in small fissures or cracks in the borehole which was prevented from being consumed in the detonation reaction; or priming system malfunction.
Various steps have been taken to limit nitrogen emissions from the sources listed above. However, even extraordinary measures to prevent release of nitrogen oxides do not fully insure that some of the explosive will not find its way into the surrounding environment. For example, NO.sub.x may be released into the atmosphere because of a less than ideal explosive reaction. It is also difficult to completely insure that nitrogen is not released into the water or ground surrounding the blasting site.
Thus, it would be a substantial advancement in the art to provide methods for blasting which did not release nitrogen into the surrounding air or water. In particular, it would be a substantial advancement to provide blasting methods which did not add to NO.sub.x emissions in the area of the blast. It would be a further advancement in the art to prevent nitrate ion from entering the ground water or land surrounding a blasting site.
Such methods of eliminating nitrogen emissions from commercial and mining explosives are disclosed and claimed herein.